I'm in the market for a rigid fork either niner, bontrager carbon, or white brothers. Anyone have any insight on which is better fork? I.E. quality, fit and finish, or weight?

I'm guilty of sometimes putting form over function, so when I choose a fork, the frame type/shape will dictate the fork options for me. I'll pair a steel frame with a steel fork or a WB carbon as they tend to match the narrow tubes of the frame. If the frame is carbon, scandium, aluminum that's oversized, hydroformed,, tapered head tube, etc. I'd consider some of the carbon fork options, like the Niner or if you want something more subtle, the Whiskey Parts carbon. There's tons of info and feedback on ride quality if you search, but the brands I mentioned tend to be the more popular choices. I like the quality of the Niner over the WB, but I've learned through my own trials that my preference is steel, and right now, I'm loving the Vassago Odis on my Jabber.

'12 Flash Carbon 29er converted to single speed. Using 120bcd 37t chainring and 23t cog allowed me to use my existing XX BB30 crankset. First tried YESS ETR-V but it wouldn't work due to interference with tiny bolts on the dropout. Settled for a Surly Singleator:

I am sure you could sell those cranks for a pretty penny and have cash left over after a purchase of a BEER EBB and a standard crank. I just put a Beer on my Cannondale Alloy 1 and it's pretty boss and allows so many more future options.